This invention relates to an air conditioner for conducting data communication mainly with a power line as a communication medium, or in particular to an air conditioner suitably used for controlling the air condition over a plurality of divided areas in a building or the like while at the same time conducting the centralized control and management of equipment and devices.
A conventional air conditioner is known which conducts communication through a power line between an indoor unit and an outdoor unit to reduce the number of wirings. In the centralized control and management of the housing equipment and devices, the power line carrier communication is conducted, and to prevent signal leakage and interference, the impedance is balanced and a high-pass filter arranged between two power lines in a power line communication area (see JP-A-7-245576).
In the conventional air conditioner comprising an outdoor unit and a multiplicity of indoor units, the indoor units are installed in a plurality of areas into which a building or the like is divided in accordance with the layout of rooms. The indoor units exchange the operating information (start/stop, operation mode, set temperature, set air flow rate, the temperature and pressure of the essential parts of the refrigeration cycle) with each other as control information and a comparatively large amount of power is consumed. Therefore, it is difficult to reduce the leakage signal which deteriorates the effective transmission rate. In the case where the open signal of the expansion valve transmitted from the outdoor unit to the indoor units is delayed, for example, the refrigeration cycle may not be normally controlled.